I run the BimmerWorld Performance/Track Engine Mounts in both my race car & street 330Ci. They fit & work great, I perceive NO new noise or vibration (but you may) with these stiffer mounts. Forum sponsor BW makes a great product, I'd recommend these to anyone looking for an upgraded motor mount.

I've been running these same mounts in my car for several years now and have been extremely happy with them. The car does "jump" quite a bit for a split second at startup until all the cylinders have started firing and they do transmit an ever so slight increase in engine growl into the cabin but otherwise they're hard to differentiate from stock in terms of noise and vibration - although you are more likely to notice if the car is running a bit rough as you'll start to feel some extra vibration in the cabin. There's just enough noise and vibration over stock to add a little character to the car without offending your passengers but they really do keep the motor fixed firmly in place relative to the stock non-M mounts (the M mounts are only slightly stiffer than the non-M and the BW mounts are significantly stiffer than both). For anyone looking for a civilized upgrade over the stock mounts, I'd highly recommend these.

I should also mention that they don't seem to compress down as much as the stock fluid filled mounts so they cause the motor to sit a few mm higher than stock. For most this won't be an issue but since my ESS TS already makes the fuel rail sit ever so slightly higher than stock, I can't fit the stock plastic fuel rail cover under my current strut tower bar (so I ditched the fuel rail cover).

I also gave a set of poly mounts a try for a few weeks and the vibration at idle with the A/C running was horrible plus there was a very nasty buzzing within the cabin when accelerating around the 2000-2200 rpm range. While acceptable for a track car, poly and solid mounts aren't really a good choice for a street car that sees much use.